Intermittent Fasting Calculator

Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. It doesn't specify which foods to eat, but rather when you should eat them. During fasting periods, your body depletes glycogen stores and shifts to burning fat for energy, a process called metabolic switching. After about 12-16 hours of fasting, the body enters a deeper state of ketosis and increases autophagy (cellular cleanup). Popular protocols include 16:8 (16 hours fasting, 8 hours eating), 18:6, and 20:4. Benefits may include weight loss, improved insulin sensitivity, enhanced cellular repair, and increased longevity markers.

Beginners should start with the 12:12 or 14:10 protocol, which are easier to adapt to. The 12:12 schedule (12 hours fasting, 12 hours eating) can be as simple as finishing dinner by 8 PM and eating breakfast at 8 AM. After 1-2 weeks of adaptation, you can progress to 16:8, which is the most popular and well-researched protocol. The 16:8 schedule offers significant metabolic benefits while remaining sustainable long-term. More advanced fasters may try 18:6 or 20:4, but these require more discipline and may not be suitable for everyone. Listen to your body and adjust based on your energy levels, hunger, and lifestyle.

During fasting periods, you can consume zero-calorie or very low-calorie beverages: water (plain or sparkling), black coffee (no cream or sugar), plain tea (green, black, herbal), and water with lemon or apple cider vinegar. These won't break your fast. Avoid anything with calories including cream, milk, sugar, artificial sweeteners (debated), bone broth, or any food. Even small amounts of calories can trigger an insulin response and interrupt the fasting state. Stay well-hydrated as thirst can be mistaken for hunger. If you must have sweetener, use it sparingly and be aware it might reduce some fasting benefits.

While intermittent fasting is safe for most healthy adults, it's not recommended for everyone. You should NOT practice IF if you are: pregnant or breastfeeding, under 18 years old, have a history of eating disorders, are underweight or malnourished, have type 1 diabetes, or have certain medical conditions without medical supervision. People with type 2 diabetes, on medications, with low blood pressure, or with a history of amenorrhea should consult healthcare providers before starting. Athletes with high training volumes may need modified approaches. Always start gradually and monitor how you feel. Discontinue if you experience extreme fatigue, dizziness, or other concerning symptoms.